1. Field of the Invention
The present invention relates to a backlight module. More particularly, the present invention relates to a backlight module with an upper filtering apparatus so that a larger proportion of a light source can operate under a better working temperature.
2. Description of the Related Arts
In recent years, techniques of manufacturing liquid crystal display (LCDs) have been quickly developed to equip many electronic products, such as personal digital assistants, notebooks, digital cameras, digital camcorders, mobile phones, computer monitors, LCD TVs, etc, with LCDs. An LCD requires the light source of a backlight module to display. Consequently, the quality of the light source of the backlight module is highly related to the quality of the LCD.
Based on the light source positioning in backlight modules, backlight modules can be roughly classified into edge type backlight modules and direct-type backlight modules. Lamps of an edge type backlight module are disposed on one side of an LCD panel. The lamp lights are propagated into a light guiding plate disposed in the rear of the LCD panel to guide reflection and refraction of the incident lights, using the light guiding plate as a medium.
The direct type backlight module comprises a back bezel, a reflection panel, a plurality of lamps, a diffuser, and an optical film set. The back bezel forms a container. The reflection panel is disposed inside the container. The lamps are arranged in the container and are disposed on the inner side of the reflection panel. The diffuser is disposed on the inner side of the lamps, while the optical film set is disposed on the inner side of the diffuser. The optical film set usually comprises a prism, a diffuser sheet, or a brightness enhancement film. The LCD panel is disposed on the inner side of the optical film set. The assembly of these components results in a complete LCD.
The temperature of a lamp surface influences the quality of a direct type backlight module greatly. Understandably, different types of lamps have different ranges of optimal working temperatures. If there are more lamps with temperatures that fall within the range, the luminance of the backlight module is more uniform, resulting in a longer lamp life. However, the heat generated by the lamps increases the temperature inside the backlight module, so fewer lamps are able to operate at their optimal working temperatures. Furthermore, since hot air rises, lamps disposed in the upper areas suffer from higher temperatures. This causes serious damages to the overall lighting quality and lifetime of the lamps.
In the prior art, an opening is disposed on the back bezel of a backlight module to release hot air. Although this method can reduce heat, no more adjustments can be made after the opening is disposed. Furthermore, external dust and extraneous particles may easily fall inside the backlight module through the opening, reducing the quality of the backlight module.
In response to the above-mentioned concerns, an invention that (1) reduces the hot air in a direct type backlight module, (2) prevents external particles from entering and changing the temperature distribution of the lamps and, (3) increases both the overall light efficiency of the light sources and the usage life is greatly needed in this field.